The optical impression of objects or of the surfaces thereof, particularly surfaces on motor vehicles, is greatly determined by the surface properties thereof. Since the human eye is suitable only to a limited extent for the objective determination of surface properties, there is a need for aids and apparatuses for the qualitative and quantitative determination of surface properties.
Surface properties such as, for example, gloss, orange peel, colour, macrostructure or microstructure, image sharpness, haze, surface structure and/or surface topography and the like are determined.
Furthermore, coatings which contain so-called effect pigments are enjoying great popularity in recent times.
The prior art discloses apparatuses in which a radiation device emits radiation onto the surface to be analysed and the radiation reflected and/or scattered by this surface is received by a detector and evaluated. These apparatuses operate satisfactorily and allow objective classification of the surface in question.
However, particularly when using the abovementioned effect pigments, the problem arises that said effect pigments may change their optical impression as a result of different physical causes. For example, it is possible that an incorrect application of paint to the surface may lead to the situation where the layer thicknesses are different at different points. The concentration of colour pigments at different areas of the surface is also accordingly different. As a result of such changes, the colour impression of such a surface will also change.
In addition, however, incorrect orientations of the abovementioned effect pigments may lead to colour changes of the surface. Ideally, these effect pigments are oriented uniformly in a given direction and in particular in the plane of the surface. However, incorrect orientations of the individual effect pigments or of groups of effect pigments may occur, i.e. individual or several pigments are rotated with respect to other pigments. In such areas, therefore, the light will also be reflected differently than in the case of uniformly oriented effect pigments.
However, the observer is unable to determine the physical causes of colour changes and is therefore unable to take any suitable counter-measures.